Polypyrrole coated magnetite nanoparticles from water based nanofluids

Abstract

The synthesis and characterization of hybrid structures obtained by coating Fe3O4 magnetic nanoparticles from water based nanofluid with a polypyrrole (PPy) layer are reported. The thin amorphous layer of polypyrrole surrounding the crystalline magnetic core was observed by HRTEM. The FTIR spectra of the nanocomposites show that the absorption bands characteristic for pyrrole ring vibrations significantly shifted to lower frequencies in the nanocomposite spectra, which indicates a higher degree of oxidation of the PPy shell covering the magnetite as compared with conventional PPy. The existence of superparamagnetism in the investigated nanocomposites is evidenced by the missing hysterezis loop in the magnetization versus applied magnetic field dependences. The comparison between the physical size of nanoparticles determined from TEM analysis and the magnetic size deduced from magnetization measurements is discussed. The surface modification of magnetite by polypyrrole coating results in an increase in the saturation magnetization and of the apparent magnetic diameter of the nanoparticles. This novel effect is attributed to a charge transfer process from the conducting polymer to the surface iron ions of magnetite, producing an increase in the surface contribution to the overall magnetic moment of the nanoparticles.

Interface charge transfer in polypyrrole coated perovskite manganite magnetic nanoparticles

“…19 The continuous lines represent the best fit based on the following equation: 20 diameter), H is the applied external magnetic field, and f(D m ) is the distribution of diameters (usually a lognormal distribution is considered). The calculations were performed following the method presented in Turcu et al 12 The data fit was realized selecting, for instance, only points corresponding to the increasing magnetic field from the M(H) dependence. By utilizing decreasing magnetic field data, the results of the fitting process were the same.…”

“…It should be noticed that the same type of increase of M S has been reported for the oleic acid coating and PPy coating of magnetite nanoparticles, respectively. [5][6][7][8][9][10][11][12] It seems that the attachment of organic molecules to the surface of magnetic nanoparticles could induce a reduction of the surface spin disorder resulting in an increase of the saturation magnetization values.…”

“…In the case of the PPy coating of magnetite nanoparticles, 12 the process was correlated to a charge transfer process arising from the conducting polymer to the surface iron ions of magnetite. It involves the laterally delocalized p electrons of the conjugated PPy that could penetrate under the surface of nanoparticles.…”

“…4,5 By adjusting the coating layers, one can induce changes in the nanoparticles' surface spin disorder and interparticle interactions; this results in different values for the characteristic parameters like saturation magnetization, coercitivity, and magnetic anisotropy of the nanoparticles obtained by different procedures. [6][7][8][9][10][11][12] In this work, we report the synthesis and characterization of novel core-shell hybrid organic-inorganic nanostructures, consisting in the deposition of a conjugated polymer layer on the magnetic La 0.67 Sr 0.33 MnO 3 (LSMO) nanoparticle surfaces. We focus especially on the polymer nanoparticle interface-properties' relationship and optimization of the nanocomposites physicochemical characteristics to make them suitable for biotechnology.…”

Linking applicatory functions to the 3-position of pyrrole by click chemistry

“…[6][7][8][9][10][11][12] Amongst nanoparticles magnetic nanoparticles have attracted wide interest in nanotechnology and nanomedicine. 13,14 The scope of polypyrroles can be considerably extended when functions, such as reactive groups, biological recognition functions, ligands for metal complexation, or catalytic units are introduced.…”